Ball-tip writing instrument and ball therefor



1965 I H. R. FEHLING ETAL 3,166,050

BALL-TIP WRITING INSTRUMENT AND BALL THEREFOR Filed May 17, 1960 5 Sheets-Sheet 1 14v vaNTOks 4 6 Palm/0RD Fsuuua E ARD HENRY H/mvay 37 I MAMA 5 H. R. FEHLING EYTAL BALL-TIP WRITING INSTRUMENT AND BALL THEREFOR Filed May 17, 1960 Jan. 19, 1965 5 Sheets-Sheet 2 Fig, 6

EDWARD Han/Ry Mm r B7 3 f Jan. 19, 1965 H. R. FEHLJNG ETAL 3,166,050

BALL-TIP WRITING INSTRUMENT AND BALL THEREFOR Filed May 1'7, 1960 5 Sheets-Sheet 4 9 lo Mural ra s h /w Eli/ammo Ffim-wq 8 4&0 Hum-r HA EY r v E M Jan. 19, 1965 H. R. FEHLING ETAL BALL-TIP WRITING INSTRUMENT AND BALL THEREFOR 5 Sheets-Sheet 5 Filed May 1'7, 1960 'Hans Reinhard FehlingyZug, Switzerland, and

. porous.

United States Patent O BALL-rte WRITING nss'rngmvmnr AND 7 BALL 'rrmnanon Y Henry Harvey, Finchley, England, assignors to LRJC. Limited, London, England, a company of Great Britain Filed May 17, 1960,8913 No. 29,638

Claims priority, application Great Britain May 119,- 19 59 7 1a Cim'rns. c1. tee-42.4

This invention concerns writing instruments of the balltip type wherein the writing extremity o'r nib comprises a writing ball rotatably housed in'a socket r housing which provides a base" seat or other thrust bearing (against which the ball may thrust during the writing operation) and is so shaped'that the ball cannot drop out when the instrument is lifted'from the'writing surface, the ball being supplied with ink from a reservoir by way of a small bore feedduct. leading to the back of the ball so also 'transient as such a-finish' is rapidly destroyed or 1 altered by the abrasive action Edward of the paper on the ball during writing. a The production of the ball certain circumstances it may produce abetter trace.

But' such a surface has a degree of roughness'whi'ch is apt to increase the wear of the softer nib-material and, therefore, is selfdefeating. Proposals have been made to burnish such a lapped surface in order to diminish or eliminate this cutting action and restore a spherical- While shape over a large fraction of the ball surface. this is feasible it also tends to reduce the improvement,

. if anyy'in the trace to that of a satin finish.

v i 'Hence the' designers of ball point pens=desirousof obtaining a deep continuous trace and unable to'do so by a 7 increasing the ink carrying capacity ofthe ball, had" that as the ball is rotated by beingmoved over and I in.

contact with 'a writingsurface (such, for 'example,'as.a

sheet of papler) ,a thin film of ink is carried by'the ball'f through the narrow gap between and housing and is deposited as a writing trace on said surface. In general, the bearing surfaces of seating 's'urfacesprovided in the housing for theball. are part spherical and comprise a part-spherical lateral seatingjsurrounding the ball in the region of or above the ball equator and a part-spherical base seat. The base seat may be circumferentially continuous, or it may be discontinuous being divided by at least one-ink channel or groove leading outwards from .the end' of the feed duct; it may merge, without interruptiominto a part of the lateral seat disposed below the ball equator or may be separated from that part by a ball encircling cavity; the ink channel, or

I each of them, may communicate with this cavity. Typical designs of housing are shown in British patent specificalions Nos. 564,172 and 609,817.

Practical considerations in'an instrument intended for writing by hand on paper render it desirable to use a writing ball which is not less than 0.75 mm. and not greater than 1.25 mm. in diameter, and the great'majority the thickness of the ink filmemer-ging from the housing, a

and. to facilitatethe entrainment of air into the housing with the re-entering'surface of the balljwhen the partly or-wholly denuded of ink. a p Hence,'while the trace'deepens with anincreasedclearance, common'faults like the'accumulation of surplus ink to fall back on methods of .widening thejinitial clear-,

'ance'between theball and its housingand todevelop' v inks of very highdye concentration (up to 40percent);

and of correspondingly high.optical'density.

While generally. muchlmore successful than roug 7 balls, largeinitial clearances have 'othe'r drawbacks; In

the first place, great skill and exceptional tool maihtenance is needed to produce them reliably in the large quantities nowrequired by the writing public. 1 But the intrinsic disadvantage of a large clearance. lies in the" greater freedom of eccentric movement or displacement of the'ball within the housing and its-spherical bearing sura faces. This freedom tendsto increase the differences in' latter is on the rimof the nib ("spottingj.messiness) and the in;

terruptions'in the continuity of the/trace, particularly on changes in the direction of the stroke (skipping) are more difficult to avoid. 'Many users will also object that such a pen'will Write too freely in the sense that the ex'-.

of ball pens in useat present employ a'highly polished, preferably stainless, steel ball of 0.8 Ito.:l.0 rnrn:v diameter.

As the uniformity of the writing trace largely depends on the uniformity of the clearance between the rotating ball and its seating surfaces in the housing, particularly the lateral seating, balls for ball point pens have. to be manufactured to a maximum deviation from true sphericity of not more than :(LOOOS rnrn. The production of a mirror polish-on the ball surface is, therefore,

highly desirable in order to facilitate and maintain this extreme accuracy in mass production. 7

It has long been known that such a polish might be undesirable in use as the film of ink breaks up more easily on such a surface and the ball itself'has a greater tendency to skid .on the writing surface. It has also been suggested that a roughened or pitted ball would assist'in conveying ink from the interior of the housing to the writing surface.

' Many proposals have, therefore been made to use.

tremely small friction created by the movement of the ball during writing induces a lack of control resulting in v bad handwriting.

It is one object of the these difficulties by creating a ball with-a substantially increased ink-'carr ying capacity but without the drawbacks mentioned. Therefore, as viewed from one aspect, the present invention provides a writing ball, suitable for use.

in the writing extremity of a ball-tipwriting instrument of the type specified, consisting of a sphere whichhas craters of substantially uniform area dispersed over its whole surface; preferably, these craters should not be substantially larger in diameter than 70 microns and not sub stantially smaller than 10 microns. Preferably, for a 1 mm. ball, the craters should take up-abouthalf of the ball 7 surface and have a diameter'between 30 and '50 microns balls the surface of which is roughened, pitted, striated or satin But the improvement in writing performance is surprisingly. small, and

equipped with a cratered writing ball having the features or about one-tenth to one-hundredth the diameter of the ball, whereas the remainder'of the surface should be truly spherical and have a very high finish.

It is another object of the invention to provide an im-.

in or for an instrument of the. type specified, incorporating a writing ball of" proved writing extremity. or ni increased-ink-carryingcapacity and therefore .the inven-.

tion, as viewed from another aspect, provides a writing extremity in or for an instrument of the'type specified,

specified in the preceding paragraph, the arrangement being such that theguan't'ity. of ink deposited. on a writing surfacein normal writing is increased by at least 5,0;percent when compared with'anuncratered ball of'jhelsame, sizeinthesamenih.

a r 3,156,050 I Patented J an.;19, 1 ,96 5

r a surface correspondingto a fine lapf is also possible without difficulty. In

present invention to overcome T It is" a: further b cr'br I v method of manufacturing writing ballsof'increased-ink rsingle spark ;of predetermined electrical energy. Preferably the individual spark .is produced: by the discharge ;This"will be more e ball po p Q an is retained i it obtaining the desired trace j. greater easeo f'vvriting and a more liberali inkfflo w,falso q' a V V I V .1 x the invention to provide anew carrying capacity. Therefore, the invention,' as viewed Writing ball for a writing'instrument of the-typespecified dispersed over the whole'surface of the electrically con from a further aspect, provides in the manufacture of'a ducting ball, such craters being formedindividuallysbya of a condenser of predetermined;capacitance,, said condenser beingautomatically recharged in aknown manner from a supply of direct current at constant voltage. r

' a One of the principal objects of the present invention is to provide-means by'which the quantity of ink transferred s by theball from" the interioref the housing to'the, writing 1 surface canbe substantially increased :withouthaving to; 7 increase the radial clearance between the ball surfaceand its'spherical bearing surfaces in the housing;*But it has been-found that this objectwill only be'fully achieved by;

the present inventionlif careeis taken. to select theyrightff t i combination'between crater viscosityof the ink.

size; sluiface coverage and jthe" s H asily appreciated byeirarnining th'e factors determining the thickness until aproper spherical bearing surface is produced on the agethicknessof 0 .l -to i 0.2 'niicron gvvhich is much too;

Various methods ag rhereforefbeen developedfin the past 10" increase this :jclearance 'by a second operation; But itj has been the general experiencethatiwhile this greatly reduces the stiffness of the ball point" pen it can H not openiupthe cIearanceato produce a trace .of. more than 0.5 to 0.6 micron without defor'rning thegspherical shapeof the internal bearings produced-in the firstgoperation'. Suchiadeformationresultstinan inferior non uniformtrace; 1

I 25 of anink'trace produced a efiiciency of the creaters'as inkica'rriers decreases as the V jfreason 'isalmost' certainlythewinabilit'y ofthe ball to empty the crater; of inrapid contact with,tlie -writingsurface if .the viscositygis too Experiments with present types-of ink show that if theviscos-ity. is. increased, f

above 200 poises at roorntemperature (temperature of t writing), ball cratering becomesinetfectiveg -aswill be f illustrated by the following exampleffor standard nib with'. V

' Viscosity at temperature V nessinrnicronszv s s s heusingaby peininfgirollingf swaging. or: spinning the rim overithe surfaceof theball low! a value to produce afully-acceptableuniformtrace.

45 1 polnt nk, the following; sets of cond tions all produced a {trace thickness of about 1 micron, i. e; the same relatiyeg;

All thesermethods have one thing incommon; thatethe i trace thickness is almost entirely Ide'pendent on: the; ballfl clearance; -whereas the influence er .the viscosity'g withiri i the acceptable'range, is small." As there is always a 'cer-' tain degree of slip between the ball surface andjthe' writ ingsurfa cejin the act of jwriting; the'transfer of ink from;

'the former'to thelatter is at least partly.donebyawiping '7 7' a ,k V l The presentinvention adds to the carrying capacity' ef.

'- the clearance that of the craters. The 'capacit'ylof the 'craters canbe'increased to at least twice that of clear-- ance by increasing the surface coverage of the craters.

" and/ or theirindividualsize. Trace thicknesses have thus been=increased to as muchfa's 2.0 .microns,.vvhich'is in. 4

fact considerablymore than is required' for'most. pur

poses, There is, therefore; a vvide freedom of cho ice for thickness Without any .detenorationiniits quality.

On the: other hand,the transferiofink from the craters" to the writing surfacejwill be mainly by a rather. than a wiping action... For this reasongthe. in- ,j fluence'of theviscosityiscoiisiderable. Y

'Th'e inks at present used in. satisfactory ball point clotting? 7 withuncrateredballshave a viscosity of. not less than about.80 l00"poises at 6. (correspondingdoabout:

. 300-400 poises at lSf Cfaiid lO-SO poises atl C 7 It? 5 7 has been found that a lower viscosity, vi'qhileproducing"a1 Correspondingviscosity at" a r'efei'c 7 increases the .objectional tendency of and consists of depositing aniad'ditional drop or spbflbf ink when the tracecliangesitS direction rather sharply as in the upper loop of the letter e.

;I t has'now been'f ound that this tendency -practicallyz; V vanishes over the whole viseositylrangefrom 10 poises' T upwards when createdballsl are used according to thef invention;- 7 On theiother hand, it was also found thatthe viscosity increases within the 'saine viscosity'range. The

1 balls}? (a) Uncratoredbfall (b) Cratcre'di ball (40% coverage, cra- {1.0 9:85 imahighes thickness.

In order t of, present daynibseby at least :In the aboveex It "will be appr e rflt w if the-surface coverage and the lcraterdiarneter is increased, the same l increases in consumption as'in the above examplecould be obtained withhigher viscosities. For a typical iball increase in in}; consumption by; t'o %;over a good 1% standard nib with} an -uneratered ball-of 1 mm, diameter Surface coverage oicraters,percent 35 40 50 Condenser capacityin circuit used to 3 ,craters, mfd 0. 03 0. 1 0. 25. Average crater dimensions: 7 V

Diameter, microns; 25' 1 40 50' Deptlymicronsg.-- e -f- '5. 0 5. 7

Ink carrying capacity ef'c'raters in terrnsoi 7 equivalent film thicknesson a smooth ball,

microns 0. 6 0.8 1. 0' Approximate average distance apart of craters, .7 V

microns.' i V 15 20* 17 *Approxirnatc number oferatcrstperballutflnt 2,200. 1,000. l S00 7 Ink viscosityat the average temperature of V V 4 writinr poiscs i 25 1 '80 While there is, therefore, avvide choice of conditions" .Which can be selected to achieve a certain result. and which can also be controlled'in manufacture, the .following'ranges are preferred: I v l fiurface coverage of craters between-iit) and 50%. Crater, diameter.between 3O andSO microns.

C. ofanink for useii i 1(a) temperate climate (r 1 between wand 30 poisest (b). ;hot climate (room tenip iYVifl'iBQZtild-ZOU poises.-

a pen topro I duce-visible irregularities in. tl'ie arnount. of deposited I alongthetrace. -One such fault is known as spotting:

Theses results are generally:achievedby sele ting thet t inkviscosit which will stillgivethef desired trace V d complete uniformity in thefi depth, i of the. trace along' its length;(n'o visible-surplus 'or de fi ciency ef ink it .is desirabletoincrease theconsumption Ink'v'iscosity at the'tempe'rature" of writing-between 40 nee temperature ch25? oorii temperature 15 C." )r i Iatnre of writing.

taken .on the line IHIII in FIG. 2;

1G.- 4 is a sectionalview through a single craterprior uncratered surface.

poises at C.

These ranges have so far givenjthe best all-round performance fora normal ball point writing instrument with (-1) The handwriting characteristics as well as the prefer ence of individual Writers, whichvary widely;

(2) The physical nature of the writing surface, in particii.-

lar its absorption characteristics.

From this aspect, the invention consists in a ballpoint pen having a nib with a cratered'ball and'a reservoir charged with a suitable. ink the viscosity of'which does" not exceed 200 poises at the normal temperature of use in writing. Preferably'the 'o'fll should have craters of a diameter between and 50 microns covering between 30 and 50% ofthe ball surface and' 'the'inkshould have a In order, that the invention ings in which:

FIG; 1" shows, partly in acrateredball according to this invention; a

' .FIG. 2 isascctional View of the relevant portion of'fa' to removal'of the burrf around'its edge, and

, FIG. 5 is a'plan 'viewtof the crater; Y

v 1 may be -betterl unclerstt'qod, reference willnow' be made to the ac'companyihg draw.

section and partly in elevation,

scale,

V ink is indicated at l5.

ball 1 according to the'invention and an essentialjfeaturel of the construction is shown' in FIG. 3 on agreatly en larged scale. The nib itselfmaybe die-cast inQtin alloy,

the ball 1 between the base seat and the lateral seat. The

As shown in FIG. 5, between the smooth spherical surface 3 of the ball and the lateral seat 5 there isya radial V clearance or gap ltl through which ink iscarriedin shear by the rotation of the ball. gIn addition, the craters 2 carry ink bodily from the housing to the writing surface irrespective of the sizeot the nadial clearance. p ,1

The importance of this will be better appreciated from Elbe following'consideration: V o V V V g 1 As the ink 'film filling the radial clearance 10 is sheared viscosity range of 40 tolOQ poises at ,tnenormal ternper- .FIG.: 6 is. aidiagram of a suitable arrangement for Y :carrying out the spark erosion method of this invention FIGS. 7A and 7B jointly show, in sectional elevation apparatus according to this invention;

FIG. 8 is a sectional. plan view thereof partly broken. J

taken on the line VIII VIII in FIGSQ7A and away,

FIG. 9 showsa detail;

FIG. 10 is a section talgen on but on a larger scale; a

a FIG. 11 shows the electrical circuit; and- FIGS. l2 and 13 show a modification of the apparatus. FIG. 1 illustrates acra-tered ball 1 of approximately 1.

mm. diameter. The craters 2 are distributed at random may be highly polished or have a satin finish.

the line Xi-1min rrol 7A,

once ithas emerged from the housing; is Tonly halfas thick (excluding cratersy as the film filling-the clear-{ Qn the other hand,the inkjin' the craters 2 is-not1(or 5 not to the 'same'eXtent) subject to the shear mentioned and is, v therefore, carried bodily with the "ball." Hencethe craters, though only occupying part ;of the ball surface, are very effective j ink carriers tinterms 1 of the I amount actually deposited as-a trace on the writing; surface.- The fiirtherr'advantages are thatthe amount. can, .ried infthe cratersis entirely independent of the changing radial clearance between "the ball and..its seating's and thatany surplus of ink notftaken up by the paper is 7 carried back into the housing-without being scraped off by andj depositcd onthe rim of .the housing. At the 1 a same time, the 'smallerradial clearanceof the'nib according to the invention, when compared withfia conventional nib producing the same depth of trace, together-with thev a ink retainingbharacteristics ofithe'craters, ensures that far less. air is entrained into. the interior of the nib by i the rotating ball.

FIG. -3 also explains another, and at firstsurprising,

. feature of the invention, viz; that craters as large as surface-area, but best results are obtained with a cratered area of about half the surface area. I It will be appreciated that wa balance must be kept between the ink-carrying capacity of the craters and the smooth bearin'g area of the The diameter of the craters of a 1 mm. ball should preferably be not less than 10 microns (otherwise the ink-carrying capacity of the craters be- 7 comes too small to be really useful) and not'larger than 70 microns (otherwise the local deviation from the oversurfaces is correspondingly increased and the curvature is reduced. As described above, the best results have been.

obtained with craters of 3 0-to 50 microns diameter when using a cratered steel balLof' 1 mm. diameter in' a dieoast tin alloy nib with a viscous ink of about 40 100 FIG. 2 shows a ballpoint pen nib 4 witha cratered :microns in diameter, if surrounded by a perfectly smooth;

spherical surface, donot impair those writingcharacteristics of the-nib which are conditioned by'a smooth rota- Y tionoi the ball over a well lubricated-bearing. If FIG. .3 is interpreted as an-illustration of part of a spherical base seating it-will be'seen that when-theballis pressedinto the. latter theiik in the crater is trapped by the.

matching spherical surfaces of the ball: and of the seat of forming a pressurized liquid cushion whichis, of

course,'the very condition of a lubricating film. For.

' this reason, it is not correct that a ball with 50% cratered area has thereby lost half its bearing surface. This would only betrue if'the single craters weretoo large or if they were not evenly dispersed so that a substantial number of such-craters would merge. Ont'ne other hand,

it half the surface of-a1 mm. ball" is formed accordingv to the invention by-craters inotsubstantially exceeding 50 microns in diameter, I and if the average. dimension of the-individual spherical base seatings'is not much less than 200 microns so that the ratio. ofthe. area ofeach base seat to the area of each crater is greater, than about twenty to one; it can be shown that more than half of the craters within the base seat area take full part4" forming the lubricating film supporting the ball; r

H by these known methods;

x l Taking] such a: nib (with unci atered poli 'FIG.'j4'shows, in? sectio n' a 'typical' c atei" This will .be appreciated fromj t h e following] results 7 given by ay offex ample. In conventional'nibs fireball J isi'etained in its housing by peining or spinning, i.e., thef'r-in'r encircling theball is pressed onto the ball either;

by 'a 'single blow using a conical die or by continuous pressure exerted by a setof rollers. Due to elastic' rey v c oivery a very small butuniforih radial clearancebetween theflpoli sh'ed' uncratered ball ancl' its 's'eati'ngs is: formed I Sucha clearance is diflicult,

i to measure directly but in'the case ofa specific exampleof -peined nib is about 2 to 3 micronswhen deterrnined I by the bubble pressure method described in British patent specification No. 629,283. Tests of a particular specimen with an uncratered polished ball and a,viscous ink of" I, about 80 'to O1poises at" C.on a writing machine producingja continuous traceatwa-speed of 8 cm. per i second andf.170 grain 'loadon the nib; show the average. thickne ssfof the ink film'bn ordinary, writingpapehxto be approximately 0.0001 irnrnl' 0.1" micron) ;j-

afbasisfor comparison, theuse of- 'a erater'ed ball ma 'increasegby atleast halffand-aoftenas muehas four-told: the-amountioff ink depositedro'n thewriting surface under" otherwise identical; conditions.' Bearing ih'rm'nd-what- 3' has'fbee'n said-above, thisindicatesrwhy' the depth, the. regularity ahdf the-continuitvof the trace areisofniuch "Ito the extent desired,withfa'multiplicityoffsingle 'c raters q of substantially uniform size; j The craters arfe 'thorou'ghly; f

improved,

h'ed Baily;

"area-Q50,

trically conductive ball toi t efl 1 dissipated, during the electrical discharge tends. to repel the:

ball frointhe rollersiand; 'because'of the change in orienration of the ball'c'ausedi by rotation of'the rollers, a subsequent dischargeoccursat a different point on the surface. 'of the ball. 'But though the'circuit is so designed that the condenser is capable ofa spark frequ'encyfof many' thousands per,;second,;tl1e 'arrangernent is such that; in all but exceptional:gcircumstances, only one single discharge "occurs at a time and not a rapid succession of a multiypllcityfof discharges: I

V 'The'fundamental reason for this:behaviorfis that the ball 1 is completely free to move away from the electrodes. 14, ISZunder, any 'force acting on it. It is, therefore,

thought that ,the explosive nature of the spark'whichno 16 supplies the force which ejects the ball from the proxter,therefore, only occurs when the ball falls back onto throughje'resion bya single spark f 1 1G15 shows plan view of sucha cratejr-i: By' ayS fQeXample; acrate'r' of ab' out microns diameter and approximately 5 m i 1 (i ns depth is produced in astainless steel ball 0511 m; 1 diametei fby {the single discharge off a condenser having f- ;a capacitance ora microfaradlcharged to:40 vol ts, w ith parafiin" oil at room, temperatureias a dielectric liquid.

Experimentsindicate that theiyolunie of inetall'erodecli'nfforrning a single cra'ter is: proportional to the electrical energyffof'a'singlefdischarge of the' 'jcondenser;

capacitance" oft-0.01 microfaradi at l40 -voltsr p l v craters .of'approximately- 15"microns*diamterjanda capacitance of =l.0-rnicrofarad atig40 :ydltsQProdticIes it craters ofiapproximatelyflll micronsdiar'neterif 91 Thus a over its-surface facilitated.

a r V t I 'Asiillu'strated in PIG -i,thisparlethroWS-HPal thin;

burr 1l arourid the" crater 2: The material forming this ffburr" lies above the level or. the 'sphericalsurface 3 but 'as'it is very brittle'it' cah be easily removed any 7 I suitable fdeburring method, e g; rolling, between 'hard' platesytumbling', lapping, polishing, or the like,fl T 1 FIG, 6 showsschematicallyaLsuitable-arrangemeht for '50 t i c r I by gearin'g;28.' The balls 1 which havea diameter larger I than the gap between therollersH-and15 aresupplied to producing a crater'edball bya successioii of single spark dischargesfl A direct ciirrenflsupply of 'electricity eg -a fat: '40'volts, is connected to "the circuit at 20, 21 Eandf" fis'fed through 'a resistance'lz to a,-cond enser l3 acting as the store iii-electrical energy. The' output from the condenser is coupled to a pair of electrodesfl lia'nd l5 7 consisting of parallel rollers 'rotating -as {indicated at a" speed'of, for example 15 r.p.m. "-Tl Je rollers maybe of brass and have a diameterjof one-half to three-quarters of an'inch; they areseparatedby a gap of say' 0.020 inch (0- when p g a1 m ball.- Th'ey are many immersed in a liquid dielectric 16 such :as parafiih'joil. fScrapers 17,18 made of electricallyinsulating material.

and'running the fulllength of the rollers preventjthe ball ltobe treated from being carried aw a'yjby the rnovement ofithe-liquid or'ofthe rollers :when' the: latter are r'otating.

The pumpinga'ction of the rollers assists in preventingjthef v i .70, the ballclose to the face j 1 1 ball from short circuiting the gap betweensthein andf-induces a teetering movement of of each roller; f

insuflicient to'prevent an electrical :discharg'e taking place As each'balllapproaches thero llers 14, 15 itiea ch'es e' apointwhe're the dielectric strength of the liq'uid i6 is i doubt vaporizes, a minute quantityof thedielectric liquid Q imity of the roller surface, thus increasing the gap beyond v fthe breakdown limit for the vsubsequentspark. The lat-Q hargesj- 5 I to, talreplacet Thus, aftera glven'tirne' the ballisfcoyerei,

[distributed, 1but-in asomewhat random manner, over-the 5 whole exterior of; the ball "so as-;to reticulate its spherical" is'ur'fac el 'Hereand there two adjacent craters mayjmerge but substantiallyall of them areindividually surrounded f V by the smooth outer'surtaceof theballf/Tl'ieir 'si zedej pends on the applied voltageiandthejcapacityof the con-f, denser? A' successionioflballsmay be treatedby rolling them along the gap between the electrodes in which nib-J tiori each ball is rotated and the d wheel gearing26 and the two rollers-are geared together tribution of the craters V In the apparatus ShOVl/Illll FIGS? 7A to 10, two parallel rollersl land 15 are rotatably, journaledlin non-conductf ingjerid plates l2g'23connected in spaced relation-by-"dis- I j .,tance rods Z4. The rollersrotate in the direction ofythei c I,

- arrows Sh0W1iin FIGSIO' With a small gap between them, i

being driven-from electricnriotor 25. Convehientlxlthisf' t motor 25 "drives the roller 15 through wormiandworn1' the rollers from a magazine 29 byga feedf'pipe 30.: They;

' are supplied at appropriate intervals by a-rotatable pickup disc 311 in-the base of the-magazine 29, said pick-up r 7 disc having spaced ball-receiving notches-or pockets32in cits periphery and being driven from"motor"'25 or another: motor by gearing comprising eIfiductiongear boX 3i3'andequal bevel vgears 33't' Y As shown in FIG. 7A

34, The scrapers 17T and l8' consist-ofnylon filaments strung-between theend plates 22,f -23.- The inclinationof the rollers ensures that the-balls pass 7 l the base of the magazine 29 and. a

the pick-up disc 31 are 'inclined. In the-lower part of the: magazine the'balls l 'insert themselves'into the recesses 32 7 and are carried up to a higher point at which each recess;

" injturn registers. with the entryend of tube 30 so that each ball'gravitates fromits recess down the tube to the I gap between the two rollers. V

. conveniently at an angle of 1 or 2, so that, as they rotate in the direction of the arrows (FIG. 10) the balls '1 roll:

- in spaced relationfalong-the ro11ers until at the left-hand end of the. apparatus" they pass down a discharge spout The rollers are inclined,

alongthe rollers from right fto" left as viewed in FIGSI 7A and 7B, ultimately, to enter the discharge spot 34 and" -15 by; asprin'g co'ntact 39. V I t a The rollers" 14,15 may rotate at the same or slightly fall into a receptacle provided for the purpose; The precise angle of inclination of the rollers determines how long 1 each ball stays on the rollers-which period maybe of V the order of: several minutes. There is sometimes a tend ency, especially when large condensers are used, for the. ball to adhere slightly to'one or other ofthe rollers afteran electrical discharge. Therefore, in order to prevent such a ball from being carried away from the gap between the rollers, the scrapers 1'7 .and 18 are providednear the surface of each roller as shown; in FIG. Thes e scrapers rub. against the surface of therespective roller and pick up any adherent balls'otf the surface of the rollers in order that they may fall back towards the gap and undergo further cratering. l

Current is supplied through -leads'20,= 2 1' connected toterminals 36, 37 which Ys upply the. respective rollers 14, 15 through brush gear. For each'roller the brush gear may berof the form shown in FIGJ 9 in relation to the roller 15.; It "consists; of a brush; 38f supplied from 2oterminal 37 by, and pressed against the end of roller different peripheral speeds; the two rollers rotate-atspecific example the peripheralv speed of rollers 14 is 24 feet per minute and that of roller 15 is feet per minute, and the balls 1 (being 1 mm. diameter) are supplied at an approximate rateof one per second. For this'purpose the rollers are 0.680 inch diameter, themotor 25 rotates at 3400 r.p.m., the ratio of'reduction gearing 26 is 25 :1

and that of reduction gearing 28 is 6:5, the ratio of gear 1 box 33 is 900:1, and the pickup disc 31 has sixteen.

pockets 32. The rollers 14, 15 may be 15 inches long. I This apparatus is intended to be supported. in a bathof liquid dielectric 16 such as p'arafliin, for example, the level of which is such that therollersare totally immersed. V

The electrical apparatus may be housed'in casing 40. As shown, it consists of a series of condensers 13a-13e,

.the capacitance of which increases steps from 0. 01

microfarad for condenser 13a to 1 microfarad for condenser Be. and a series of resistances Ila-12 the value of which decreases'in steps from 9.1 kilohms for resistances 12a to- 125.0hms for resistance. 12e, together 'witha suitable switch 41' for introducinginto the circuit the selected condenser and the resistance appropriate to it. A volt-meter'42 may be incorporated. The electrical discharge phenomenon produced by this circuit can occur at a high frequency since the condenser is capable of charging and "discharging many thousands'of times per second. With the apparatus shown, which incorporates rollers 15 inches long, there may be as many as 80 or 100 balls on" the rollers at any one instant, all of these participating in the cratering process. On rare occasions it has been found that a pair of adjacent balls have touched together during their passage. along the rollers and have consequently welded together. Thereafter, such a pair of balls have suffered cratering' in theform of bands which destroy their spherical shape. To overcome this positive means may be provided for moving the balls along the rollers while maintaining them in spaced relation, instead of allowing them to gravitate along the rollers. For this purpose, as shown in FIGS.

' surface is of the order of a few microns;

ref.

of its flanks In" aconveni'ent construction the roller. 7 I

15 has a 0:68 inchdiameter and the roller 14 has an 070 inch crest diameter. and a 0.652 inch root diameter and the-peripheral gap between the two rollers is between 0.01 inch and 0.015 .inch. QRoller 14" rotates at,120 .f

r.p.m. and roller 15 at 144-r.p.m., the ball feedbeing at the. rate of jl per second, i.e., one ball for every two revolutipnsofroller1ft.

. Although the. inventionhas been described abovewith I referenceto specific embodiments, many variations and modifications therein' willoccur tolthose shilledfin the I v art. Accordinglyfifis intended that {all'such variations. 7

and modifications be includedwithin thescope of -the following claims. 15' i We claim:

1.:A ball for a ball-tip writinginstrument-comprising a, sphere having a smooth, continuous spherical outer surface and havin'g'a pluralityof shallow craters distributed ".[subst'an'tially uniformly over the outer surface substantially all of the craters having a depth no lessthan about 5 microns and adiametier-between'about 10 -andabont 70.m ic rons and having sides inclined at; an'angle between' about-110'degrees-afid aboutZS degreesto thesurface of 5 the',sphere,-"the 'totalarea. of thecreaters being between about onefif th. and about two thirds' of the. total surface area bf the sphefe.

2. A writing extremity less than about 5 microns and a diameter between about '10 and about 70 microns and having sides inclined at an angle betweenabout 10 degrees and about 25 degrees to the surface of 'the sphere,;and awritingnib having a retaining rim with an' adjacent part-spherical lateral seat in supporting'the sphere.

. SKA writing extremity according to claim 2 wherein the maximum spacing betweenthe surface of the sphere and the closestadjacent portion of the retaining rim inner,

4. A writing extremityacco'rding to claim 3 portion ofthe retaining rim inner surface. d

5. A writing extremity according to claim 2 wherein the sphere surface.

" 6. A writing extremity for a ball-tip writing instrument if comprising a sphere having a smooth, continuo'us spheritween the rollers and therefore advances along the rollers cal outer surface and having a plurality of shallow craters r 'of substantially uniform diameter formed in the outer surface of the sphere, the total area of the craters being it between about onefifth and about two-thirds of the total 25 degrees to the surface of the sphere, a writing nib having a retaining rim with an adjacent part spherical lateral seat surrounding the sphere so as to retain the sphere 'in the Snib, the maximum spacing between the V sphere and the closest adjacent portion- 0f the retaining of thescrew thread thereby eliminating any rislr of contact between adjacent balls. For 1 mm. balls the pitch Y of this screw'thread maybe 1 mm. and the included angle rim being of the order of a few thousandths of the diam; eter of the sphere, the writing nib being formed with an.

internal cavity communicating with an ink reservoir and foraball-tip writingins'trument 7 comprising a sphere having a smooth, continuous spheri-w cal outer surface and having a plurality-of shallowcraters of substantially uniform diameter formed in the outer surface distributed substantially uniformly over the outer surface, substantially all of the craters having a depth no wherein theaverage depth of the craters in the sphere 'surfaceis x approximately the same as thev maximum spacing be-g tween the surface of the sphere and the closest adjacent v 'in'thesarnewritingnib. j s v 7. A writingextremity accordingr t of clairnu6j wherein,

the nib is .forrned with "atleast'onepart-spherioalbase? with the portion of the sfih'ere enclosed the nib to supply viscous ink to thes'urface 'of the. sphere .and the craters therein, whereby the quantity of viscous inkcan 'rie'd by the spherepast the retaining rim as the ball'rotates a is at least fifty percent greater thani the quantity of ink carried by a similar} ball haying nocrater mounted:

seat closely adjacent to the sphere, the area i of the f base seat adjacent to thesph'ere being at least about twenty times the area.ofithefindividual craters'in the sphere so that the Viscous :ink' from the cavity-which I passes bea 1 tween the-sphere and the bearing surface' is trappedfin a substantial proportionof the craters adjacent to the sur face toaid in supporting the sphere. k V h -8J A writing extremity for a ball-tip writingiinstru ment comprising a sphere havinglja smooth; continuous I y sgherical outer surfacejand'having a plurality of s hallo' w r craters'ofsubstantially uniform diameter formed.- ii'rthe outer surfac'erand distributed substantially: uniformly/[j over the outer-surfaee, substantially all bf'thecratershaw' mg a depthno less than about 5 jinic rons fand a' diarneter, between aboutltl and about 70 microns and having sides inclined atan angle between abQut'lO' degreesandabont' 25 degrees to the 'surface qfthe sphere,t he total; area qf' 1/ 1 2 47 751] s ;,2;s47, 97s. 25-

I. theviscosityof the ink microns and about 5'0 mier the" craters being-between gabout,one-fifth and about two thirds of thetotal area of -thei'spherq alwritifig nib having a retaining rim with an adjacent, part;spherica1 lateral seat surrounding theispher'e and at leas't' onepart-spherical; bases'eat, the writing'nib "being formed with an internali cavity communicating with anjinkreservoiryand ais upply' r of writing ink having a viscosity;notexceedingaboutillO p oisesfat 25 C. within-thecavity and the reservoir sdthat ink'is carried by the sphere past} the retaining rim ent re j surface'of; thessphere and. bygthe craters in the surface as 1 thesphere'is rotated in'the nib; i

9.7 A writing extremity according "'.;10. A writing instruin nt-according to claim-8wherein 7' theaverage diameterftof ;the craters is between aboutfijO mismatched m me fil -t aw UNrTEDs'rAT- srATENr ,izjss'aizt',

V t Aug. 19,1958 2350518 :4

4 wi laim s herein V is between about 49 rpois'esfand 

1. A BALL FOR A BALL-TIP WRITING INSTRUMENT COMPRISING A SPHERE HAVING A SMOOTH, CONTINUOUS SPHERICAL OUTER SURFACE AND HAVING A PLURALITY OF SHALLOW CRATES DISTRIBUTED SUBSTANTIALLY UNIFORMLY OVER THE OUTER SURFACE SUBSTANTIALLY ALL OF THE CRATERS HAVING A DEPTH NO LESS THAN ABOUT 5 MICRONS AND A DIAMETER BETWEEN ABOUT 10 AND ABOUT 70 MICRONS AND HAVING SIDES INCLINED AT AN ANGLE BETWEEN ABOUT 10 DEGREES AND ABOUT 25 DEGREES TO THE SURFACE OF THE SPHERE, THE TOTAL AREA OF THE CREATERS BEING BETWEEN ABOUT ONE-FIFTH AND ABOUT TWO-THIRDS OF THE TOTAL SURFACE AREA OF THE SPHERE. 